1. Field of the Invention
The present invention is in the field of water or wastewater treatment and specifically relates to apparatus for use in destroying dissolved organic contaminants in the water or wastewater.
Hydrogen peroxide is added to the water or waste-water, which is then subjected to intense ultraviolet radiation. The ultraviolet radiation breaks the hydrogen peroxide into hydroxyl radicals which are powerful oxidants. These radicals attack and oxidize the organic contaminants which are also being broken down by the ultraviolet radiation. Applications of the apparatus include the detoxification of industrial wastewater or the complete destruction of organic contaminants in the water, the destruction of solvents, pesticides and fuels, or other organic contaminants found in groundwater, the destruction of concentrated organically contaminated aqueous wastes, and the production of high quality organic-free water for industrial processes.
2. The Prior Art
The present invention is a part of a system for treating liquids, usually water, containing undesirable organic compounds to render those compounds harmless through the action of strong ultraviolet radiation and through chemical oxidation.
The overall system includes an electrical power supply, controls, an oxidation chamber, piping and wiring, and a steel skid on which the other components are mounted. The present invention relates to the oxidation chamber. The liquid to be treated is caused to flow through the oxidation chamber.
Full-scale systems have been installed at several locations throughout the country and are operating routinely. That this system operates with high reliability and safety is attributable in large part to the engineering innovations to be disclosed below, and is particularly surprising in view of the potential hazards involved.
One model of the system is 15 feet long, 7 feet wide, and 8 feet high; it weighs 12,000 pounds. This unit can process 500 gallons per minute of liquid, and uses 425 KVA of 3-phase 480 volt electrical power. A large part of this electrical power flows through quartz ultraviolet lamps that are mounted within the oxidation chamber and that are surrounded by the liquids that are being treated. Clearly the system includes a number of potentially antagonistic elements--high voltages and currents in close proximity to liquids and powerful reagents. In a very real sense, the inventions disclosed below have made it possible for these antagonistic elements to cooperate in achieving safe and reliable operation on a scale never before attempted.
One can appreciate that the dissipation of hundreds of kilowatts in a cold pressurized liquid poses major challenges in materials selection, in accommodating thermal expansion, and in maintaining good sealing of the chamber.
The unprecedented size and power of the apparatus gave rise to a number of problems for which the prior art provided no solutions, as will be described below.
For example, in U.S. Pat. No. 3,485,576 issued Dec. 23, 1969 to McRae, et al., there is described an ultraviolet disinfection system in which a quartz lamp is in direct contact with the liquid to be disinfected, and a simple O-ring seal is provided at each end of the lamp. In contrast, the amount of power dissipated in the lamps of the present invention makes it essential that the lamps be kept from direct contact with the liquid.
In U.S. Pat. No. 4,273,660 issued June 16, 1981 to Beitzel, there is described a water purification system in which the cylindrical treatment chamber has an annular cross-section. A tubular ultraviolet lamp extends axially through the center hole. The chamber appears to be of unitary construction, and therefore localized thermal expansion will be a problem if a large amount of heat is dissipated by the ultraviolet lamp. Also, fouling of the chamber wall adjacent the ultraviolet lamp will necessitate replacing the entire chamber.
In U.S. Pat. No. 4,694,179 issued Sept. 15, 1987 to Lew, et al., there is described a device for purifying fluid media. The treatment chamber is cylindrical in shape and the ultraviolet lamp is protected from the fluid being treated by a tube that surrounds the ultraviolet lamp. End members at opposite ends of the tubular housing are said to include seals, but the sealing arrangement is neither shown nor specifically described. If the drawings are indicative, the device does not appear to be able to withstand an appreciable amount of thermal expansion of the tube surrounding the lamp, rendering this approach unsuitable for use at high power levels such as those used in the apparatus of the present invention.
Thus, the known prior art does not appear to provide satisfactory approaches for use in the present large-scale high power apparatus wherein multiple lamps are operated in a rectangular chamber.